JP2003015587A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce moving image pseudo contours that occur in a non-edge area where gradation change is hardly caused in a subfield division drive type display device. SOLUTION: A non-edge area extracting part 7 detects non-edge areas of an image, a gradation range calculating part 8 detects the gradation range in each non-edge area, a series selection control part 9 outputs a signal for selecting a subfield series with no carry gradation included within the gradation range in each non-edge area, a code conversion selecting part 13 selects a code- converting part using the signal, and the code conversion selecting part 13 performs imaging processing of a field pattern by subjecting it to code conversion so as to reduce the moving image pseudo contours in each non-edge area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a plasma display panel (hereinafter referred to as PD
The present invention relates to a sub-field division drive type display device which expresses gradation by dividing one field into a plurality of sub-fields, which is represented by a device such as P: Plasma Display Panel.

[0002]

2. Description of the Related Art FIG. 13 is a block diagram showing a main structure of a conventional display device, such as a display device 100 disclosed in Japanese Patent Laid-Open No. 10-116053.

In the figure, 1 is an input terminal for inputting a video signal, 2 is an input terminal for inputting a synchronizing signal, 3 is an A / D converter for converting the video signal input to the input terminal 1 into a digital signal, Reference numeral 18 refers to a sync signal as a reference
/ D conversion unit 3, field memory unit 14, and drive unit 15
Is a control unit for controlling. Reference numeral 11 is a code conversion unit that performs code conversion of the output of the A / D conversion unit 3, and 14 is the code conversion unit 1.
A field memory unit that stores the output signal of 1 for two fields, 15 is a drive unit that drives the PDP 16 by the output signals of the field memory unit 14 and the control unit 18, and 16 is P
It is DP.

Hereinafter, the operation of the conventional display device 100 configured as described above will be described. The video signal input from the input terminal 1 is converted into an 8-bit digital code signal by the A / D converter 3. This digital code signal has 256 gradations from 0 to 255.
Assuming that the bits of the digital code signal are b7, b6, b5, b4, b3, b2, b1, b0 in order from the most significant bit, the respective bits are 128, 64, 32, 1
It has a weight by the relative ratio of powers of 2, such as 6,8,4,2,1.

The code conversion unit 11 converts an 8-bit digital signal into a code having a number of bits larger than 8 bits in order to reduce a moving image false contour phenomenon as described later. However, if no measures are taken against the moving image pseudo contour phenomenon, the code conversion unit 11 is not necessary and the 8-bit digital signals b7 to b0 may be directly input to the field memory unit 14.

Therefore, first, the operation in the case where no countermeasure against the moving image pseudo contour phenomenon is taken will be described. The field memory unit 14 stores the digital signals b7 to b0 for two fields. There are two field memories in the field memory unit 14, and the input signal is written alternately in the first memory and the second memory for each field.

FIG. 14 is a diagram showing a light emission sequence in the case where no measures are taken against the moving image pseudo contour phenomenon in the conventional display device. As shown in the figure, one field period is divided into eight subfield periods SF0 to SF7, and each subfield period is divided into an address period and a sustain discharge period, which will be described later.

Under the control of the control unit 18, bit b0 data for all pixels are sequentially read from the field memory unit 14 in the address period of the subfield period SF0 shown in FIG. At this time, the field memory unit 14 having two fields is read from the one in which the writing operation is not performed. That is, in each field memory, writing is performed on one side and reading is performed on the other side during one field period, and these operations are alternately repeated in each successive field period.

The data of the bits b0 for all pixels read out in this manner are sequentially passed through the driving unit 15 to the PDP1.
Written in 6. PDP 16 is an AC with memory function
The memory effect holds the data of each pixel until the data for all pixels is written. Next, the control unit 18 controls the drive unit 15 to set P
Among all the pixels of DP16, only the pixel of which the stored bit b1 is "1" emits light for a predetermined sustain discharge period.

In the address period of the next subfield period SF1, the data of bit b1 for all pixels is sequentially read from the field memory unit 14 and written to the PDP 16 through the driving unit 15 in the same manner as the above-mentioned SF0. Be done.
In the subsequent sustain discharge period, similarly, only the pixel in which the bit b1 is “1” emits light. Where subfield period S
The sustain discharge period of F1 is twice as long as the sustain discharge period of SF0, and the light emission time is twice as long as SF0.

Similarly, for the subfield periods of SF2 to SF7, the corresponding bits b2 to b7 are written to all the pixels of the PDP 16 in the address period of each subfield, and in the subsequent sustain discharge period. Pixels whose respective bits are "1" are caused to emit light. The light emission time of each subfield, that is, the relative ratio of the sustain discharge period is made to match the relative ratio of the weights of the corresponding bits. That is, when the emission time of SF0 is 1, SF2, SF3, SF4, SF5, SF6, SF
The luminous time of 7 is 4, 8, 16, 32, 64, 1 in order.
28 becomes a power of 2 and becomes longer.

By emitting light as described above, when the light emitting time of each pixel is summed for one field period, the light emitting time for the gradation corresponding to 8 bits of the digital data b0 to b7 is obtained. When a person views the PDP 16, it is recognized that each pixel is emitting light with a gradation of 8-bit display capability of digital data b0 to b7 due to the integration effect in the time direction, and 256 gradation display is performed. Will be realized.

In such a display device in which one field is divided into a plurality of sub-fields for display, when a flat image whose gradation changes smoothly is moved on the screen, the gradation is changed in the image. A band-shaped portion that is brighter or darker than the surroundings, or a band-shaped colored portion is perceived. These phenomena are phenomena called moving image pseudo-contours, which are unique to moving images that cannot be seen when the image is stationary, and are a major factor that deteriorates image quality when displaying moving images on a display device such as a PDP. Has become.

The principle of generation of the pseudo contour of the moving image will be described below with reference to FIGS. 15 and 16.

In FIG. 15, an image whose gradation changes smoothly on the screen of the PDP, that is, an image whose gradation changes from 127 to 128 is directed to the left in the horizontal direction at a speed of 2 pixels / field. It is a state explanatory view showing a moving state. FIG. 16 is a diagram showing the relationship between the retina position and the amount of perceived brightness when a human sees this image. Note that FIG.
The horizontal axis of represents the pixel position of each line of the screen arranged in the horizontal direction, and the vertical axis represents the passage of time.

In this case, in the gradation 127 part, SF0
7 to SF6, light is sequentially emitted in seven subfield periods, and in the portion of gray scale 128, the subfield period SF7
It is emitting light only. On the other hand, when a human sees such a changed image, the line of sight follows the changed portion and moves approximately along the broken lines R0 to R1 shown in FIG. As a result, as shown in FIG. 16, the position on the retina corresponding to the left side of the broken line R0 is the gradation 127,
The position on the retina corresponding to the right side of the broken line R2 is the gradation 128.
Will be perceived. However, the perceptual amount of the position on the retina corresponding to the broken line R1 becomes almost 0, which is perceived as a false contour.

This phenomenon is caused by SF0 to SF as described above.
An image that changes from the gradation (127) in which seven of 6 emit light to the gradation (128) in which only SF7 emits light, that is, carry from the lower bit to the most significant bit, and vice versa. Images that carry down from bits to lower bits are more likely to be perceived when moving. This is due to the following two points.

(1) The temporal center-of-gravity variation of light emission in the field period is large between adjacent gray scales. That is, in the gradation 127, the light emitting portions are concentrated in the front part in the field period, and the gradation 1
28 is concentrated in the rear. (2) The amount of change in the sustain discharge period in each subfield period, which changes from the non-light emitting state to the light emitting state and from the light emitting state to the non-light emitting state, is large between adjacent gray scales. That is, the sustain discharge period from SF0 to SF6 corresponding to 127 changes from light emission to non-light emission, and SF corresponding to 128
The sustain discharge period in No. 7 changes from non-light emission to light emission.

An example of measures taken in the conventional display device configured as shown in FIG. 13 in order to reduce the deterioration of the image quality due to the moving image pseudo contour as described above will be described.

The video signal input from the input terminal 1 is A /
The D conversion unit 3 converts the 8-bit digital code signal (b0 to b7), and further, in the code conversion unit 11,
It is converted into a code signal having more than 8 bits.
Here, the case of conversion into 9 bits will be described as an example. The code conversion unit 11 receives the 9-bit digital code (bb0, bb1, bb2, bb3, bb4, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5, bb5.
6, bb7, bb8) are output. The digital code converted by the code conversion unit 11 is hereinafter referred to as a subfield pattern. The converted sub-field pattern is stored in the field memory unit 14 for two fields.

The following gradation display operation will be described with reference to FIG.
Will be explained. FIG. 17 is a diagram showing an example of a light-emission sequence in one field period in the case of taking measures against a moving image pseudo contour in a conventional display device. One field period includes nine subfield periods SF0 to S
The gradation is expressed by displaying the image by dividing it into F8. Here, each subfield period SF0 to SF8
Are the subfield patterns bb0 to bb, respectively.
Corresponding to each bit up to 8. As in the case of FIG. 14, the subfield periods SF0 to SF8 are divided into the address period and the sustain discharge period.

Under the control of the control unit 18, the data of bit bb0 for all pixels are sequentially read from the field memory unit 14 during the address period of SF0 shown in FIG.
At this time, as described above, the field memory unit 14 having two fields is read from the one in which the writing operation is not performed. After writing the sequentially read out data of the bits bb0 for all pixels into the PDP 16 through the driving unit 15, the sustain discharge period starts. The control unit 18 controls the driving unit 15 during this sustain discharge period, and of all the pixels of the PDP 16, only the pixel of which the bit bb0 is “1” emits light.

Similarly, for each subfield period of SF1 to SF8, the corresponding bits b1 to b8 are written to all the pixels of the PDP 16 in the address period of each subfield, and in the subsequent sustain discharge period. Pixels whose respective bits are "1" are caused to emit light. By emitting light in this manner, the total of the light emission time of each pixel for one field period is recognized by a person who views the PDP 16 as a gradation.

Here, the relative ratio of the sustain discharge period (light emitting time) of each subfield is 1: 2: 4: 8: 16: 32: 48: 64: 80 in the order of SF0 to SF8.
And includes subfields with a ratio that is not a power of two. When all subfields emit light, 1 + 2 + 4 + 8 + 16 + 32 + 48 + 64 + 80 =
There are 255 gradations, and there is a display capacity of 256 gradations from 0 to 255 depending on the combination of emission and non-emission of each subfield.

The code conversion unit 11 performs code conversion so that the gradation of the digital data (b0 to b7) before conversion and the gradation displayed by the subfield pattern (bb0 to bb8) after conversion match. Is going. The contents of this code conversion will be described below.

Considering the example of FIG. 14 in which the code conversion is not performed, in this case, the emission weight of the subfield is 2
Since the digital data itself corresponds to a subfield pattern, there is only one type of subfield pattern that expresses a certain gradation. For example, the subfield pattern expressing the gradation 64 is (b7, b
6, b5, b4, b3, b2, b1, b0) = (0,
1,0,0,0,0,0,0) only, and gradation 1
The subfield pattern expressing 28 is (b7, b
6, b5, b4, b3, b2, b1, b0) = (1,
0,0,0,0,0,0,0) only.

On the other hand, when the code conversion is performed as in the example of FIG. 17 and the subfield of the emission weight which is not a power of 2 is included, that is, bb is sequentially arranged from the most significant bit.
8, bb7, bb6, bb5, bb4, bb3, bb2, bb1, bb0
Each bit of 80, 64, 48, 32, 16, 8, 4,
When the weighting is 2, 1, there are a plurality of sub-field patterns for expressing one gray level. For example, the subfield pattern (bb
8, bb7, bb6, bb5, bb4, bb3, bb2, bb1, bb
0) has two types, (0,0,1,0,1,0,0,0,0) and (0,1,0,0,0,0,0,0,0), Also, subfield patterns (bb8, bb7, bb6, bb5, bb4, bb3, bb2, bb2, bb2, bb2, bb2, bb2, bb2, bb2, bb2, bb2, bb2,
1, bb0) is (0,1,1,0,1,0,0,0,
0), (1,0,1,0,0,0,0,0,0) and (1,0,0,1,1,0,0,0,0).

When there are a plurality of subfield patterns for expressing a certain gradation, the code converting section 11 selects an appropriate one subfield pattern from among them. Gradation 0 to maximum gradation (25 in this example)
Each series obtained when the subfield patterns set for each gradation up to 5) are arranged and seriesd is hereinafter referred to as a "subfield series" or simply "series".

In the conventional display device, the pseudo-contour of the moving image is reduced by using the following rule when determining this sequence.

In gradation n (0≤n≤254), the bit bbx having a weight greater than or equal to a relatively large weight (32 in FIG. 18) is "1", and the bit having a weight one level higher than bbx. In the gray scale in which carry of the bit occurs such that bby is “0” and bby is “1” in the gray scale (n + 1), the bit bbx of the gray scale (n + 1)
To "0". Hereafter, this rule is referred to as "carry rule".
Call.

FIG. 18 is a pattern diagram showing an example of a sequence configured to satisfy the above-mentioned carry rule.
In the figure, the area shown in the hatched area is "1" in the display state.
The non-hatched area indicates "0" in the non-display state. Further, the weight is shown by the width of the column so that the weight of each bit can be easily understood. Figure 1
In 8, bits having a weight of 32 or more satisfy this carry rule.

The effect of reducing the perceived amount of the false contour of the moving image by using this sequence will be described with reference to FIGS. 19 and 20.

FIG. 19 shows that an image whose gradation changes smoothly on the screen of the PDP, that is, an image whose gradation changes from 175 to 176 is directed to the left in the horizontal direction at a speed of 2 pixels / field. It is a state explanatory view showing a moving state. Further, FIG. 20 is a diagram showing the relationship between the retina position and the perceived amount of brightness when a human sees this image. Incidentally, FIG.
The horizontal axis of 9 corresponds to the pixel positions aligned in the horizontal direction of each line on the screen, and the vertical axis indicates the passage of time.

The subfield period SF8 having the largest relative ratio of the luminance (proportional to the sustain discharge period) is the gradation 175.
No display is made in the area of, and a display state is made in the area of gradation 176. At this time, a carry state to the so-called most significant bit is shown. When a human sees such a changed image, the line of sight follows the changed portion, and moves approximately along the broken lines R0 to R4 shown in FIG. The position on the retina corresponding to the left side of the broken line R0 will perceive the gradation 175, and the position on the retina corresponding to the right side of the broken line R4 will perceive the gradation 176. R1 and R in the meantime
The perceptual amount of the position on the retina corresponding to 2 and R3 is as shown in FIG.

As described above, the code conversion unit 11 (see FIG.
3) is added to take measures against the motion picture pseudo contour,
5 and FIG. 16, it is understood that the change in the perceived amount of brightness is reduced as compared with the case where the countermeasure for the moving image pseudo contour is not taken.

This includes 48 and 80 subfield periods in which the relative ratio of the sustain discharge period (light emission time) deviates from a power of 2, and the subfields are arranged in ascending order (or may be in a large order). Further, by using the series that follows the carry rule described above, the temporal center-of-gravity variation of light emission in the field between adjacent gray scales is reduced.

Another factor is that the amount of change in the sustain discharge period in each subfield period in which the light emitting / non-light emitting state changes between adjacent gray scales is relatively small. For example, between the gradation 175 and the gradation 176, 1, 2,
A total of 79 of 4, 8, and 64 changed from light emission to non-light emission, and
0 changes from non-light emission to light emission. In the case of FIG. 15 before the above-described countermeasure, when the gradation 127 changes to the gradation 128, 127 changes from light emission to non-light emission and 128 changes from non-light emission to light emission.

As described above, in the conventional display device, the subfield period having the sustain discharge period whose relative ratio is not a power of 2 is included, and the temporal arrangement of each subfield period indicates the relative ratio of the sustain discharge periods. By adopting the order of increasing or decreasing and following the above-mentioned carry rule, the temporal centroid variation of the light emission in the field between adjacent gray scales becomes relatively small, and the gray scale between adjacent gray scales decreases. As a result, the amount of change in the sustain discharge period of each subfield that changes from the non-light emitting state to the light emitting state and from the light emitting state to the non-light emitting state also becomes small, and the perceived amount of false contours in a moving image is reduced.

Further, in the conventional display device, the pseudo contour of the moving image is reduced by switching and displaying a plurality of subfield sequences.

FIG. 21 is a block diagram showing the configuration of another conventional display device 101 shown in the above-mentioned Japanese Patent Laid-Open No. 10-116053. The same components as those of the display device 100 shown in FIG. 13 described above are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

In the figure, 1 is an input terminal for inputting a video signal, 2 is an input terminal for inputting a synchronizing signal, and 3 is an A for converting the video signal input to the input terminal 1 into a digital signal.
A / D conversion unit, 12a performs code conversion of the output of the A / D conversion unit 3 based on one of the two series, and a code conversion unit A, 12b outputs the output of the A / D conversion unit 3 to two series. It is a code conversion unit B that performs code conversion based on the other of the series.

Reference numeral 13 is a code conversion selection unit for selecting and outputting either the code conversion unit A12a or the code conversion unit B12b in accordance with the output signal of the control unit 18, and 14 is the output signal of the code conversion selection unit 13 for two fields. A field memory unit for storing the minutes, a drive unit 15 for driving the PDP 16 by the output signals of the field memory unit 14 and a control unit 20 to be described later, 16 for the PDP, 20 for the A / D conversion unit 3, a code based on the synchronization signal. The control unit controls the conversion selection unit 13, the field memory unit 14, and the driving unit 15.

The operation of the conventional display device 101 configured as described above will be described with a focus on the differences from the conventional display device 100 shown in FIG.

The code conversion unit A12a is the code conversion unit 1 in the conventional display device 100 shown in FIG.
A / D based on the sequence A of the same subfield sequence as 1
The digital output signal of the conversion unit 3 is code-converted. On the other hand, the code conversion unit B12b performs code conversion based on the sequence B having a bit pattern of a carry gradation to an upper bit different from the sequence A according to the above-described carry rule. FIG. 22 is a pattern diagram showing an example of the series A and the series B. The series A shown in FIG. 22A is the same series as that shown in FIG. 18, and the series B shown in FIG. The carry pattern to the higher order bits is different from that of the series A, while following the carry rule of.

Then, the code conversion selection unit 13 outputs each output signal from the two code conversion units 12a and 12b, that is, each subfield pattern, every h pixels (h ≧ 1) in the horizontal direction of the screen, and on the screen. Every v pixels in the vertical direction (v ≧ 1)
Has been switched to. Other operations are the same as those of the conventional display device 100 shown in FIG.

Such a conventional display device 101
In the above, the moving image pseudo contour is further reduced as compared with the display device 100 using only one subfield sequence, as will be described later.

FIG. 23 is an operation explanatory diagram showing a display state in series B when an image whose gradation changes smoothly on the screen of the PDP changes under the same conditions as in the case of FIG. . FIG. 24 is a diagram showing the relationship between the retina position and the perceived amount of brightness when a human sees the image of FIG.
Note that the horizontal axis of FIG. 23 corresponds to the pixel positions aligned in the horizontal direction of each line on the screen, and the vertical axis indicates the passage of time.

In the series B, the bit pattern of the carry gradation to the upper bits is different from that in the series A as described above.
Between the gradation 175 and the gradation 176, the display state (light emitting state) of the subfield period SF8 having the largest relative ratio of the sustain discharge period and SF7 immediately below it does not change, and the change of the display state is low. Stays in the subfield period. When a human sees such an image, his or her line of sight moves approximately along the broken lines R0 to R2, but the perception of false contours at positions on the retina corresponding to R0, R1, and R2. The amount (generally proportional to the magnitude of the level decrease) is, as shown in FIG. 24, the series A shown in FIG.
Compared to the case of.

FIG. 25 is an explanatory diagram showing which selection is used to display each pixel on the screen by the series A or series B subfield pattern.
Here, as shown in the figure, when the series A and the series B are switched and used at relatively narrow pixel intervals, such as every pixel in the horizontal direction and every pixel in the vertical direction, the human vision 26, the pseudo contours of the moving images perceived by the series A and the series B are averaged as shown in FIG.

Comparing this with FIG. 20, it can be seen that the false contour of the moving image is reduced as compared with the case where a single sequence is used. This example shows the case of two series, but 3
Even when three or more series are switched and displayed, the averaging is similarly performed, and the moving image pseudo contour can be reduced.

[0051]

In the conventional display device constructed as described above, the sub-field series that reduces the shift of the light emission center of gravity in the field is used, and the light emission luminance (proportional to the sustain discharge period) is used. The pseudo contour of the moving image is reduced by switching and displaying a plurality of subfield sequences having different carry patterns to the upper bits corresponding to the larger subfield.

Actually, the pseudo contour of a moving image is conspicuous when an image satisfying a specific condition is input, but the conventional display device performs the same processing regardless of the input image signal. Therefore, the reduction effect is limited.

Further, the temporal center-of-gravity variation of light emission, which is the main factor of the pseudo contour of the moving image, is caused by the carry to the upper bit corresponding to the subfield having the higher light emission luminance. It was impossible to prevent the carry to the upper bit.

The present invention has been made to solve the above problems, and by performing processing according to an input video signal, the emission luminance (corresponding to the sustain discharge period) under specific conditions can be improved. An object of the present invention is to provide a display device by suppressing carry to the upper bits corresponding to a large subfield.

[0055]

According to another aspect of the present invention, there is provided a display device, in which gradation values of pixels are sequentially weighted by a predetermined relative ratio by a u-bit digital code, and one field period emits light according to the relative ratio. In a display device which is divided into u sub-fields having a period and each pixel in which corresponding bits in each sub-field are in a predetermined state is caused to emit light for gradation display, the relative ratio does not follow a power of 2. And a code conversion means capable of digitally converting the gradation value into a selected subfield series among a plurality of subfield series having different carry gradation values. Assuming an image based on a video signal, a non-edge region that detects one or more non-edge regions whose gradation changes gradually in each predetermined range is detected. Area detecting means; gradation range calculating means for sequentially detecting and storing the maximum value and the minimum value of the gradation of each pixel in each non-edge area for each of the non-edge areas; Of the sub-field sequence, within the gradation range of the non-edge region being processed that is determined by the maximum value and the minimum value, the carry gradation exists in each bit whose weighting by the relative ratio is a predetermined value or more. In order to preferentially select the sub-field sequence, the sub-field sequence selecting means for controlling the code converting means and the gradation value of the input video signal are sequentially input, and the processing is performed according to the selected sub-field sequence. A signal delay means for delaying the input grayscale value by a predetermined time and outputting the grayscale value to the code conversion means so that each grayscale value of the non-edge region in the inside is digitally coded. To.

The display device according to claim 2 is the display device according to claim 1.
The display device described above is characterized in that the plurality of subfield sequences are two sequences. According to a third aspect of the present invention, in the display device according to the second aspect, the carry gradations in the two series are configured to appear alternately in magnitude of the value. A display device according to a fourth aspect is the display device according to the first aspect, wherein the plurality of subfield sequences are three or more sequences. A display device according to a fifth aspect is the display device according to any one of the first to fourth aspects, wherein the predetermined range is one field. A display device according to a sixth aspect is the display device according to any one of the first to fourth aspects, wherein the predetermined range is one line. The display device according to claim 7 is the display device according to claim 1.
In the display device described above, the code conversion means includes a plurality of code conversion units that digitally code the input grayscale values in different subfield sequences, and
It is characterized in that it comprises a code conversion selecting section for selecting one code converting section, and outputs a digital code digitalized by the selected code converting section. Further, the display device according to claim 8 is the display device according to claim 1, wherein the subfield sequence selecting means cannot find a subfield sequence in which the carry gradation does not exist within the gradation range. The code conversion means is controlled so as to sequentially select the plurality of subfield sequences for each predetermined pixel unit.

According to a ninth aspect of the present invention, the display device according to the ninth aspect uses the p-bit digital code in which the gradation value of each pixel is sequentially weighted by a predetermined relative ratio by the code conversion means, and one field period is a light emitting period according to the relative ratio. With p
In a display device in which each pixel is divided into subfields and each pixel has a corresponding bit in a predetermined state to emit light to display a gradation, when an image based on an input video signal is assumed, Non-edge region detecting means for detecting one or a plurality of non-edge regions having a gentle change in tone, and the maximum and minimum of the gradation of each pixel in each non-edge region for each non-edge region. A gradation range calculation means for sequentially detecting and storing the values, and a gradation range of a non-edge region being processed which is determined by the maximum value and the minimum value, each of which is weighted by the relative ratio to be a predetermined value or more. When there is a carry gradation in bits, the carry gradation is not included in the corrected gradation range obtained by correcting the gradation value of each pixel in the non-edge region being processed. To correct the gradation value And having a gradation correction means for outputting said code conversion means Te.

A display device according to a tenth aspect is the display device according to the ninth aspect, in which the gradation correction means sequentially inputs the gradation values of the input video signal and delays them for a predetermined time and outputs them. And a gradation correction unit that corrects the gradation value delayed by the signal delay unit based on the gradation range and the value of the carry gradation. A display device according to claim 11 is the display device according to claim 10,
The gradation correction unit corrects the difference between the maximum value or the minimum value of the gradation and the value of the carry gradation by adding or subtracting the difference to the input delayed gradation value. . Also,
13. The display device according to claim 12, wherein in the display device according to claim 10, the gradation correction unit inputs only the difference between the maximum value or the minimum value of the gradation and the value of the carry gradation. The gradation value is corrected so as to compress the gradation range of the generated gradation value. The display device according to claim 13 is the display device according to claim 1 or 9, wherein the non-edge region detecting means detects an edge portion where the gradation of an image sharply changes, and the edge detecting portion. And a non-edge region extraction unit that extracts a non-edge region in which the brightness or color changes smoothly based on the edge information from the detection unit.

[0059]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing a configuration of a display device 50 according to a first embodiment of the present invention. The same components as those of the conventional display devices 100 and 101 shown in FIGS. 13 and 21 are designated by the same reference numerals.

In the figure, 1 is an input terminal for inputting a video signal, and 2 is an input terminal for inputting a synchronizing signal. Reference numeral 3 is an A / D conversion unit for converting an input signal input to the input terminal 1 into a digital video signal, and 4 is an A / D conversion unit 3 and a carry according to the synchronization signal input to the input terminal 2. The control unit controls the suppression processing unit 5, the signal delay unit 10, the field memory unit 14, and the driving unit 15, respectively. A carry 5 outputs a subfield sequence selection signal for suppressing a carry of a subfield described later according to the digital video signal A / D converted into an 8-bit digital code by the A / D converter 3. The suppression processing unit includes an edge detection unit 6, a non-edge region extraction unit 7, a gradation range calculation unit 8, and a sequence selection control unit 9, which will be described later.

Reference numeral 10 corresponds to a signal delay means, which is a signal delay unit such as a memory for delaying and outputting the digital video signal by the amount corresponding to the processing time in the carry suppression processing unit 5. Reference numeral 12a is a code conversion unit A for converting the digital video signal input from the signal delay unit 10 into a subfield pattern of a certain sequence and outputting the coded sub-field pattern. A code conversion unit B that performs code conversion into a subfield pattern of a different sequence from the conversion unit A12a.

Numeral 13 selects one subfield pattern from the two subfield patterns input from the code conversion unit A12a and the code conversion unit B12b based on the subfield sequence selection signal input from the carry suppression processing unit 5. It is a code conversion selection unit to output. 14
Is a field memory unit for storing two fields of the subfield pattern input from the code conversion selecting unit 13, 15 is a driving unit for driving the PDP 16 by the output signals of the field memory unit 14 and the control unit 4, and 16
Is the PDP.

In the carry suppression processing section 5, 6
Is an edge detector for detecting edges of the video signal,
Is a non-edge region extraction unit that extracts a portion that is not an edge (hereinafter referred to as a non-edge region) in the video based on the detection result of the edge detection unit 6, and 8 corresponds to a gradation range calculation unit, and the non-edge region Is a gradation range calculation unit that calculates the maximum value and the minimum value of the gradation of the image, and 9 corresponds to the subfield sequence selection, and is a floor in the non-edge region obtained by the gradation range calculation unit. It is a subfield sequence selection unit that generates a subfield sequence selection signal for suppressing a carry to an upper bit based on the maximum and minimum values of the key.

The code conversion unit A12a, the code conversion unit A12b, and the code conversion selection unit 13 constitute a code conversion unit, and the edge detection unit 6 and the non-edge region extraction unit 7 constitute a non-edge region detection unit. There is.

Next, the operation of the display device 50 will be described.

In the A / D converter 3, the video signal input terminal 1
The analog video signal input from is converted into a digital video signal by an 8-bit digital code.

The edge detection section 6 performs edge detection in order to separate the digital video signal A / D converted by the A / D conversion section 3 into an edge portion and a smooth portion. For example, the difference in the gradation value between the adjacent pixels is calculated, and when the difference value is larger than a predetermined threshold value, it is determined as an edge, so that the edge in the image can be extracted.

The non-edge area extraction unit 7 determines, based on the edge detection result, a non-edge area when a predetermined number of non-edge pixels in one field continue in the horizontal and vertical directions. . Since there are usually a plurality of non-edge regions in one field period, each non-edge region is numbered sequentially from 1. This number is hereinafter referred to as a region number.

In the gradation range calculation section 8, the maximum gradation value and the minimum gradation value among the gradation values of all the pixels in each non-edge area are assigned for each area number assigned by the non-edge area extraction section 7. The gradation value of is calculated. This processing requires the longest processing time in the series of processing of the carry suppression processing section 5. This is because the grayscale values of all the pixels in the same non-edge region are required to calculate the maximum grayscale value and the minimum grayscale value. The processing time of one non-edge region is longest when all the images of one field are one region, and the processing time corresponds to one field period.

Here, the gradation range calculation unit 8 is constructed so that the processing time is constant regardless of the number of regions in the field. FIG. 2 is a circuit block diagram showing the internal configuration of the gradation range calculation unit 8. The gradation range calculation unit 8 will be described below with reference to FIG.

In the figure, reference numeral 31 is a FIFO (First In First Out) buffer which sequentially stores the area numbers of the pixels currently being processed and has a capacity corresponding to pixels for one field. Reference numerals 32a and 32b are registers for reading and writing the maximum gradation value and the minimum gradation value using the area number as an index. Reference numeral 33 denotes a changeover switch for switching access to the registers 32a and 32b for each field.

34 is a register 32 based on the current pixel area number and gradation value input from the non-edge area extracting section 7.
a is a maximum / minimum gradation value updating unit for updating the maximum gradation value and the minimum gradation value in the register 32b, and 35 is a FIFO
Using the region number one field before read out from the buffer 31 as an index, the maximum gradation value and the minimum gradation value of the non-edge region including the pixel one field before are read from the register 32a or the register 32b and the sequence selection control is performed. It is a maximum / minimum gradation value reading unit for outputting to the unit 9.
With this configuration, it is possible to always output the calculation result one field after the input to the non-edge region extraction unit 7, as described later.

The two sets of registers 32a and 32b are provided in order to calculate the maximum gradation and the minimum gradation and hold the calculation result up to the next field. For example, in a certain field period, by connecting the changeover switch 33 to the A side, the register 32a is used as a work register for calculating the maximum gradation value and the minimum gradation value of the current field. At this time, the register 32b is read-only, and the maximum gradation value and the minimum gradation value one field before are read from here.

In the next field, the changeover switch 33 is set to B.
The side connection is performed and reading is performed from the register 32a, and the register 32b is used as a work register.
By switching the changeover switch 33 for each field in this way, the register 32a is alternately alternated for each field.
And the roles of the register 32b are exchanged.

Hereinafter, the case where the changeover switch 33 is connected to the A side, that is, the case where the register 32a side is used as a work register will be described as an example.

First, the operation of the maximum / minimum gradation value updating unit 34 will be described. When the pixel currently being processed is in the non-edge area, the maximum gradation value and the minimum gradation value are read from the register 32a using the area number as an index. The read values are respectively compared with the gradation value of the current pixel. When the current gradation value is larger than the read maximum gradation value, the maximum gradation value of the register 32a is updated. Similarly, when the current gradation value is smaller than the read minimum gradation value, the minimum gradation value of the register 32a is updated. By performing the same process for all the pixels in one field, the register 32a stores the calculation result of the maximum gradation value and the minimum gradation value for each non-edge area number.

Further, the FIFO buffer 31 performs the following processing. If the pixel currently being processed is in the non-edge area, the area number is assigned to the FIFO buffer 3
Store in 1. If the pixel currently being processed is not the non-edge area, “0” is stored in the FIFO buffer 31 instead of the area number.

As described above, the area number or 0 corresponding to all pixels for one field is the FIFO buffer 3
Sequentially stored in 1. In this way, the data stored one field before is due to the characteristics of the FIFO buffer.
The new data after one field is sequentially read from the FIFO buffer 31 in synchronization with successive writing of new data.

At this time, the region number of the pixel read one field before and the maximum gradation value read one field before,
The following processing is performed using the data of the register 32b in which the minimum gradation value is stored.

If the read area number is not "0",
That is, in the case of a non-edge area, the maximum gradation value and the minimum gradation value of the area number are read from the register 32b using the read area number as an index and output to the sequence selection control unit 9. At the same time, "1" is output as the non-edge area discrimination signal. When the read result is "0", "0" is output as the non-edge area discrimination signal. At this time, since the output of the maximum gradation value and the minimum gradation value has no meaning, any may be output. In this way, the gradation range calculation unit 8 outputs the maximum gradation value and the minimum gradation value always one field period after the input of the non-edge region extraction unit 7.

Next, the operation of the sequence selection control section 9 will be described.

In the sequence selection control unit 9, the gradation range calculation unit 8
The maximum gradation value, the minimum gradation value, and the non-edge area discrimination signal of "0" or "1" output from the The gradation range determined by the gradation value and the minimum gradation value is compared with the carry gradation value of each sub-field series stored in the code conversion unit A12a and the code conversion unit B12b, and It is determined whether or not each carry gradation is included in the gradation range of the non-edge region, and the subfield sequence selection signal corresponding to the judgment result is output. This will be further described below with reference to FIG.

FIGS. 3A and 3B show the code conversion unit A1.
2a and an example of the subfield sequence stored in the code conversion unit B12b, the sequence SA is the code conversion unit A.
12a, and the sequence SB is stored in the code conversion unit B12b. In this example, the emission luminance (corresponding to the sustain discharge period) weight of each subfield corresponding to the relative ratio of the bit weight of each series is the conventional display device 1 shown in FIG.
Similar to 01, in the order of SF0 to SF8, 1: 2: 4:
The ratio is 8: 16: 32: 48: 64: 80.

As shown in the figure, the weighting of each bit of each series is performed in the corresponding subfield periods SF0 to SF.
It is expressed as the weight of the luminance of F8, and in order to avoid complication, the bits bb0 to bb8 are expressed using the corresponding subfield periods SF0 to SF8.

Black portions in FIG. 3 represent omissions. For example, in the gradation values 1 to 14 of the series SA, the subfield periods SF8 to SF4 are the same and SF
Only SF0 changes from 3 but this change is simply 000 as SF3 to SF0 as a 4-bit binary number.
It only changes from 1 (decimal 1) to 1110 (decimal 14). Similarly, with respect to the other omitted parts in FIG. 3, only the subfield periods SF3 to SF0 are changed.

In the subfield sequence of FIG. 3, since the light emission luminance weights of the respective subfields have weights that are not powers of 2, gray scale 48 to gray scale 2 are included.
In the range up to 07, a plurality of subfield patterns for displaying a certain gradation can be considered. By utilizing this property, the series SA and the series SB are configured such that there are locations where the subfield patterns are different.

Next, the carry of the subfield in FIGS. 3A and 3B will be described. Gradation n to gradation n
When a carry occurs between predetermined bits when changing to +1, the gradation n is referred to as "carry gradation".

In the case of the subfields shown in FIGS. 3A and 3B, paying attention only to the carry of the subfield having the weight of 32 or more, and carrying between the subfields having the carry from the weight 32 to the weight 48 or more. , The "carry gradation" is shown as CA1, CA2, ... in the series SA,
The sequence SB is shown by CB1, CB2, ...

The portions indicated by the alternate long and short dash lines in FIGS. 3A and 3B are the carry from the weight 32 (SF5) to the weight 48 (SF6) and the carry portion with a weight larger than that. The gradation on the dashed line is a carry gradation. The value of the carry gradation is different between the series SA and the series SB. For example, in the series SA, the gradation 63 is a carry gradation CA
1 and a carry from the weight 32 to the weight 48 occurs when the gradation 63 changes to the gradation 64. On the other hand, the series SB has no carry gradation in the range from the gradation 48 to the gradation 78, and within the range, carry does not occur in a subfield having a weight of 32 or more.

In the order of gradation, the carry SA is alternately arranged in the series SA and the series SB. Code conversion unit A12a and code conversion unit B12b
, Each have such a subfield sequence SA and a subfield sequence SB, the sequence selection control unit 9
A subfield sequence selection signal for selecting one of the subfield sequences is output to the code conversion selection unit 13 so as to suppress the carry of the subfield in the non-edge region. The method of selecting this subfield sequence will be described below.

The maximum gradation value and the minimum gradation value of the non-edge area output from the gradation range calculation section 8 are Pmax and Pmin, respectively. When processing pixels in one non-edge region, Pmax and Pmin of the same value are always output in correspondence to pixels in the same non-edge region.
If the pixel being processed is not in the non-edge area, Pmax and Pmin have meaningless values.

Maximum gradation value Pmax and minimum gradation value Pmin
To the carry gradation CAp (p = 1 to 5) of the series SA and the carry gradation CBq (q = 1 to 6) of the series SB, which carry gradation is included in the non-edge region. It is possible to determine whether or not is included. If Pmin <CX ≦ Pmax holds for a certain carry gradation CX, the non-edge region includes the carry gradation CX.

A specific example will be described below with reference to FIG. FIG. 4 is an explanatory diagram of a method of selecting a subfield sequence, in which a non-edge region in a video is extracted. The squares in the figure represent pixels, and the numbers represent the gradations of the pixels. In FIG. 4, the area has a rectangular outer shape for simplification, but in an actual image, the area is generally indefinite.

FIG. 4A shows an example in which the maximum gradation in the non-edge region is Pmax = 175 and the minimum gradation is Pmin = 144. Within this non-edge region, the sequence SA
Carry gradation CA4 = 159, Pmin <C
The relationship of A4 ≦ Pmax is established. Therefore, this non-edge region includes the carry gradation CA4. That is, when the display is performed using the series SA, a carry of the subfield occurs in this non-edge area. What is indicated by a chain line in FIG. 4A is a carry in this series SA, and when such an image moves in a moving picture, a moving picture pseudo-contour may occur at the position of the one-dot chain line. is there.

On the other hand, the carry gradation CBq (q
= 1 to 6) are all Pmin <CBq ≦ Pmax
Does not meet the relationship. Therefore, when displaying the pixels in the non-edge region, by selecting the subfield series SB, carry does not occur in the subfield having a weight of 32 or more, and it is possible to prevent the occurrence of the moving image pseudo contour. it can.

Therefore, in the case of the example of FIG. 4A, the sequence selection control unit 9 selects the subfield sequence SB so that the code conversion selection unit 13 selects the subfield sequence SB, that is, the code conversion unit B12b. Output a signal.
The actual processing in the sequence selection control unit 9 is performed for each pixel, but as described above, the maximum gradation Pmax and the minimum gradation Pmin are constant values for the pixels in the same non-edge region. Therefore, the series SB is selected in all the pixels in the non-edge region of FIG. 4A, and it is possible to prevent the occurrence of the moving image pseudo contour.

As another example of FIG. 4B, the maximum gradation of the non-edge region is Pmax = 180 and the minimum gradation is Pm.
The case of in = 149 is shown. At this time, Pmin <CA4 ≦ Pmax holds for the series SA, and Pmin <CB5 ≦ Pmax holds for the series SB. Therefore, even if either the series SA or the series SB is selected, a subfield carry occurs. Figure 4
The dashed line in (b) indicates the carry position when the series SA is selected, and the dashed line indicates the carry SB.
This is the carry position when is selected.

In order to suppress the dynamic false contour even in such a case, the sequence selection control section 9 determines that the pixel currently being processed is processed when the non-edge region includes the carry gradations of all the sequences. By referring to the horizontal display position and the vertical display position, a subfield sequence selection signal is output so that the sequence is switched every h pixels in the horizontal direction (h ≧ 1) and every v pixels in the vertical direction (v ≧ 1). . As a result, as shown in FIG.
By the same effect as the conventional display device 101 of No. 1, the light emission center of gravity position is dispersed and the pseudo contour of the moving image is reduced.

When the above example is generalized, the sequence selection control unit 9 can suppress the dynamic false contour by determining the subfield sequence selection signal so as to satisfy the following rules 1 and 2.

Rule 1: If the non-edge region does not include any carry gradation of a certain series but includes the carry gradation of another series, a series that does not include the carry gradation is selected.

Rule 2: When the non-edge area includes carry gradations of all series, by referring to the horizontal display position and the vertical display position of the pixel currently being processed, every h pixels in the horizontal direction. (H ≧ 1), the series to be selected is switched for each v pixel in the vertical direction (v ≧ 1).

When the non-edge area does not include any series of carry gradations or when pixels other than the non-edge area are displayed, any series may be selected. The series may be switched for each horizontal pixel and each vertical pixel in consideration that carry of subfields less than 32 also affects the image quality. However, in this case, there is no effect if the carry positions of the series SA and the series SB are exactly the same in the subfield having a weight less than 32.

Further, the signal delay section 10 delays the digital video signal by the processing time of the carry suppression processing section 5. The signal delay unit 10 is specifically realized by a storage device (memory) having a capacity corresponding to the delay time. The processing time from the input of a pixel P in the digital video signal to the carry suppression processing unit 5 to the output of the subfield sequence selection signal S (P) corresponding to the pixel P is T
In this case, the signal delay unit 10 delays the pixel P by the processing time T and outputs the pixel P, thereby giving the pixel P to the code conversion selection unit 13 at the same timing as S (P).

Here, in the carry suppression processing section 5, the processing time of the gradation range calculating section 8 is constant irrespective of the extraction result of the area as already described, and other processing is also included. The entire processing time T of the suppression processing unit 5 is configured to be constant. Since the processing time of the gradation range calculation unit 8 occupies the largest proportion of the delay time, the memory capacity of the signal delay unit 10 is approximately 1
It corresponds to the field period.

Code conversion unit A12a and code conversion unit B1
As to 2b, as described above, for example, the series SA and the series SB as shown in FIG. 3 are stored, and the digital video signal input from the signal delay unit 10 is stored in the series SA and the series SB, respectively. The code is converted to a subfield pattern and output.

The code conversion selection unit 13 selects and outputs one subfield pattern from the two subfield patterns in accordance with the subfield sequence selection signal obtained from the carry suppression processing unit 5. As described above, unlike the conventional display, the series selection is performed so as to suppress the false contour of the moving image according to the content of the input digital signal.

In the field memory unit 14, as in the conventional display device, the code-converted subfield patterns are alternately stored in the two field memories in the field memory unit 14. Set each bit of the subfield pattern to bb0, bb1, bb2, bb3, bb4, bb5, bb
6, bb7, bb8, first, during the address period of SF0, the field memory unit 14 is controlled under the control of the control unit 4.
From subfield pattern bit bb0 is drive unit 15
Through PDP16.

After sequentially writing bb0 for all pixels, the pixel of bb0 = 1 in the PDP 16 emits light during the subsequent sustain discharge period. Similarly, for SF1 to SF8, bb1 to bb8 are P through the driving unit 15 in the address period, respectively.
It is written in DP16 and emits light during the subsequent sustain discharge period.
Since the light emitting operation by the field memory unit 14, the driving unit 15, and the PDP 16 is the same as that of the conventional display device 100 shown in FIG. 13, detailed description thereof will be omitted.

As described above, according to the display device of the first embodiment, the carry of the subfield which causes the pseudo contour of the moving image is suppressed inside the non-edge region which is the smooth portion in the image. It is configured to do. As a result, the carry of subfields concentrates on the edge part of the image, but if the pseudo-contour of the moving image occurs in the smooth part of the image, the image quality will be greatly reduced, while at the edge part the pseudo-contour of the moving image will However, it does not cause much problem because it overlaps with the true contour.

Further, in a normal image, when only the part where the gradation changes smoothly is extracted, it is often within the range of the comparatively narrow gradation. Therefore, according to the configuration of the present embodiment, there is a high possibility that a subfield sequence can be selected so that a subfield carry does not occur in a non-edge region, and as a result, a portion in which the gradation changes smoothly In this case, carry of a subfield having a large light emission luminance can be suppressed, and a moving image pseudo contour can be prevented.

Even when the carry of the subfield cannot be prevented inside the non-edge region, the pseudo contour of the moving image is reduced by the same processing as the conventional display.
Therefore, in addition to the effect of reducing the moving image pseudo contour of the conventional display, the effect of preventing the moving image pseudo contour in the non-edge region described above works, resulting in a higher effect of reducing the moving image pseudo contour than that of the conventional display.

Embodiment 2. Although the two sequences SA and SB are used in the first embodiment, it is possible to configure using three or more sequences. Hereinafter, such a second embodiment will be described.

FIG. 5 is a block diagram showing the structure of the display device 51 according to the second embodiment of the present invention. The main difference between the display device 51 of the second embodiment and the display device 50 of the first embodiment is the configuration and operation of the sequence selection control unit 21, the code conversion unit group 22, and the code conversion selection unit 23. is there. Parts that are the same as or equivalent to those of the display device 50 according to the first embodiment are given the same reference numerals, and the description thereof is omitted.

In FIG. 5, reference numeral 22 denotes a code conversion unit group which has n code conversion units therein and which converts the digital video signal input from the signal delay unit 10 into N different series and outputs the code. And 23 selects one subfield pattern from the n subfield patterns input from the code conversion unit group 22 based on the subfield sequence selection signal input from the subfield carry suppression processing unit 5. It is a code conversion selection unit to output. Reference numeral 21 is a sequence selection control unit that outputs this subfield sequence selection signal.

The operation of display device 51 of the second embodiment configured as described above will be described. An analog video signal is input to the A / D converter 3 from the video signal input terminal 1. The operations of the A / D conversion unit 3, the edge detection unit 6, the non-edge region extraction unit 7, and the gradation range calculation unit 8 are exactly the same as those in the first embodiment, and therefore their explanations are omitted. Further, since the control unit 4 and the signal delay unit 10 are also the same as those in the first embodiment, their description will be omitted.

Although the sequence selection control section 9 of the first embodiment is configured to select either of the two sequences,
The sequence selection control unit 21 of the present embodiment selects one sequence from n sequences. By setting the series so that the carrys of the n sub-fields have different gradations, as described later, the pseudo contour of the moving image can be suppressed more effectively as in the first embodiment. It is possible to select the series.

The code conversion unit group 22 outputs n subfield patterns by converting the digital video signal input from the signal delay unit 10 by the code conversion units corresponding to each of the n series. As described above, the n series are set so that the carry gradations are different from each other.

The code conversion selection unit 23 selects one subfield pattern from the n subfield patterns obtained from the code conversion unit group 22 based on the subfield sequence selection signal output from the sequence selection control unit 21. hand,
It is sent to the field memory unit 14. After that, the field memory unit 14, the driving unit 15, and the PDP 16 operate in the same manner as in the first embodiment, and an image is displayed on the PDP 16.

Next, the operation of the sequence selection control unit 21 in the present embodiment and the effect of suppressing the false contour of a moving image will be described.

Basically, similarly to the sequence selection control unit 9 of the first embodiment, it is determined whether the carry gradation of each sequence is included in the non-edge region, and the digit in the non-edge region is determined. If there is a series that does not rise, it operates to select that series.

However, unlike the case of the first embodiment,
There may be multiple series in which carry does not occur. For example, if the number of series n is 3, the series SA, SB, S
When C exists, the series SA includes carry, but
This is a case where neither the series SB nor the series SC includes a carry. In such a case, any one of the series SB and the series SC may be selected. In addition, by displaying the series SB and the series SC by switching the series for each horizontal pixel and each vertical pixel, it is possible to suppress the influence of the carry gradation in the lower bits not considered.

As described above, according to the display device of the second embodiment, the number of selected subfield sequences is large (three or more).
In the case where a carry occurs regardless of which of the two series SA or SB is selected as in the example of (b), by selecting another series, a series that does not cause a carry can be selected. The probability of selection becomes higher, and the effect of suppressing the false contour of a moving image can be further enhanced as compared with the first embodiment.

Third Embodiment In the first embodiment, the extraction of the non-edge region is performed for each field, but by performing the region extraction for each line, the circuit scale can be further reduced. Hereinafter, such an embodiment will be described.

The display device according to the third embodiment has exactly the same basic structure as the display device 50 according to the first embodiment shown in FIG. Since only the signal processing of each unit shown as the range calculation unit 8'and the signal delay unit 10 'is different from that of the first embodiment, the difference will be mainly described below with reference to the block diagram of FIG.

The non-edge region extracting section 7'of the third embodiment
Then, when pixels that are not edges in the horizontal direction continue in one line of the screen of the PDP 16, this is determined as a non-edge region. Normally, a plurality of non-edge regions are present in one line, and therefore each non-edge region is assigned a region number as in the first embodiment.

Further, the gradation range calculation unit 8 of the third embodiment
′, The non-edge region extraction unit 7 ′ is the same as in the first embodiment.
The maximum gradation value and the minimum gradation value among the gradation values of all the pixels in the respective non-edge areas are calculated for each area number assigned in. Since the edge area is extracted line by line, unlike the case of the first embodiment, the size of the area is at most one line. Therefore, in the present embodiment, the processing of the gradation range calculation unit 8 ′ is performed. The time is approximately one line period.

FIG. 6 shows the internal structure of the gradation range calculation unit 8'in the third embodiment. FIG. 6 is a gradation range calculation unit 8 according to the first embodiment shown in FIG.
And the block configuration is almost the same. Therefore, only differences from FIG. 2 will be described. FI in Embodiment 1 of FIG.
The capacity of the FO buffer 31 is one field, but the capacity of the FIFO buffer 41 of the third embodiment is equivalent to one line. Along with this, in the maximum / minimum gradation value reading unit 35, the area number of the pixel one line before is FIFO.
The register 32a or the register 3 is read from the buffer 41 and the area number of the immediately preceding line is used as an index.
The maximum gradation value and the minimum gradation value are read from 2b. The changeover switch 33 is also changed line by line.

Further, the signal delay unit 10 'of the third embodiment.
Indicates that the processing time is approximately one line, and thus the delay is one line. The operation other than the above is the same as that of the first embodiment.

In this embodiment, since the processing is performed for each line, the effect of reducing the pseudo contour when the object moves in the vertical direction of the screen is weaker than that in the first embodiment, but the conventional display is still used. It has a higher false contour reduction effect than the device.

As described above, according to the display device of the third embodiment, the capacity of the FIFO buffer 41 inside the gradation range calculating unit 8'can be set to one line, not one field. Also, the memory capacity of the signal delay unit 10 'can be realized as one line instead of one field. Therefore, the circuit scale can be made smaller than that of the display device according to the first embodiment, so that it is possible to provide the display device at a lower cost and with improved moving image pseudo contour.

Similarly, even if the gradation range calculation unit 8 and the signal delay unit 10 according to the second embodiment are changed from the processing in the unit of one field to the processing in the unit of one line, the same effect can be obtained.

Fourth Embodiment In the first to third embodiments, the pseudo field contour is reduced by selecting the subfield sequence to be converted by the code conversion unit by the subfield sequence selection signal. In the form 4, the moving image pseudo contour is reduced without changing the subfield sequence.

FIG. 7 is a block diagram showing the structure of the display device 52 according to the fourth embodiment of the present invention. still,
The display device 50 of the first embodiment shown in FIG.
The same or corresponding components are designated by the same reference numerals.

In the figure, 1 is an input terminal for inputting a video signal, and 2 is an input terminal for inputting a synchronizing signal. Reference numeral 3 is an A / D conversion unit for converting an input signal input to the input terminal 1 into a digital video signal, and 4 is an A / D conversion unit 3 and a carry according to the synchronization signal input to the input terminal 2. The control unit controls the suppression processing unit 25, the signal delay unit 10, the field memory unit 14, and the driving unit 15, respectively. Numeral 25 is a digit for correcting and outputting the digital video signal so as to suppress carry of a subfield in accordance with the digital video signal A / D converted into an 8-bit digital code by the A / D conversion section 3. The rise suppression processing unit includes an edge detection unit 6, a non-edge region extraction unit 7, a gradation range calculation unit 8, and a gradation correction unit 26.

Reference numeral 10 delays and outputs the digital video signal by an amount corresponding to the processing time in the edge detection section 6, the non-edge area extraction section 7 and the gradation range calculation section 8 in the carry suppression processing section 25. A signal delay unit such as a memory. Reference numeral 27 is a code conversion unit that performs code conversion of the corrected digital video signal input from the subfield carry suppression processing unit 25 into a predetermined sequence and outputs the coded signal. Reference numeral 14 is a subfield pattern input from the code conversion unit 27. Is a field memory unit for storing two fields, and 15 is a P based on the output signals of the field memory unit 14 and the control unit 4.
A drive unit that drives the DP 16, and 16 is a PDP. still,
In this embodiment, the gradation correction unit 26 and the signal delay unit 10 form a gradation correction unit.

Next, the inside of the carry suppression processing section 25 will be described. Reference numeral 6 is an edge detection unit that detects an edge of the video signal, 7 is a non-edge region extraction unit that extracts a non-edge region in the video based on the detection result of the edge detection unit 6, and 8 is a non-edge region. Reference numeral 26 denotes a gradation range calculation unit that calculates the maximum value and the minimum value of the gradation of the image, and 26 is based on the maximum value and the minimum value of the gradation in the non-edge region obtained by the gradation range calculation unit 8. It is a gradation correction unit that corrects the gradation of the digital video signal delayed by the signal delay unit 10 so as to suppress the carry of the subfield in the area.

Next, the operation of the display device 52 will be described.

Similar to the display device 50 of the first embodiment, the A / D converter 3 converts the analog video signal input from the video signal input terminal 1 into a digital video signal by an 8-bit digital code. The processes in the edge detection unit 6, the non-edge region extraction unit 7, and the gradation range calculation unit 8 are also the same as those in the first embodiment, and thus detailed description thereof will be omitted, but in the edge detection unit 6, the A / D conversion is performed. Edge detection is performed from the A / D converted digital video signal by the unit 3, and the non-edge region extraction unit 7 detects the non-edge region in the video based on the edge detection result.
The gradation range calculation unit 8 calculates the maximum gradation and the minimum gradation for each non-edge region, and outputs the calculation result after a certain processing time, for example, one field later.

The signal delay section 10 delays the digital video signal by the processing time in the edge detection section 6, the non-edge area extraction section 7, and the gradation range calculation section 8. For example, like the first embodiment, it is realized by a storage device having a capacity corresponding to the delay time. As a result, the gradation correction unit 26 inputs the gradation value of a pixel from the signal delay unit 10 and, at the same time, when the pixel is included in the non-edge region, the maximum gradation value and the minimum gradation value of the non-edge region. The tone value and the tone value are input from the tone range calculator 8.

When the pixel currently being processed is in the non-edge region, the tone correction section 26 performs tone correction of the digital video signal so as to suppress carry of subfields in the region.

FIG. 8 is a circuit block diagram showing the internal structure of the gradation correction unit 26. In the figure, 43 is a carry determination unit that determines whether a carry of a subfield occurs, and 44 calculates a gradation correction coefficient Ca of the digital video signal based on the determination result of the carry determination unit. A correction coefficient calculation unit 45 is a gradation adjustment unit that adds the correction coefficient Ca to the gradation value of the digital video signal.

In the carry determination section 43, the maximum gradation value Pm
By comparing ax and the minimum gradation value Pmin with the carry gradations of the series stored in the code conversion unit 27,
It is determined whether a subfield carry occurs in the non-edge area to which the current pixel belongs. This determination is similar to the determination made by the sequence selection control unit 9 of the first embodiment, and Pmin <CX ≦ P for a certain carry gradation CX.
If max is satisfied, the non-edge area includes the carry gradation CX.

In the correction coefficient calculation section 44, based on the judgment result of the carry judgment section 43, in the gradation adjustment section 45,
The gradation correction coefficient Ca that suppresses the carry in the subfield is calculated by correcting the gradation in a minute range. Hereinafter, a method of calculating the correction coefficient Ca given to the gradation adjusting unit 45 will be described with an example.

9 and 10 are explanatory views of the gradation correction by the gradation correction unit 26. Each drawing (a) is a graph showing the brightness value before the correction, and each drawing (b) is the correction. It is a graph showing the brightness value after. Here, it is assumed that the carry gradation CX is included between the maximum gradation value Pmax and the minimum gradation value Pmin. FIG. 9 shows (Pmax-CX)> (CX
-Pmin), and FIG. 10 shows (Pmax-C
X) ≦ (CX−Pmin). Note that, for simplicity, the case of a one-dimensional image is shown, and the non-edge area is represented by a line segment (on the horizontal axis) of a certain section.

First, in the case of FIG. 9 described above, the carry gradation C
Since X is closer to the minimum gradation value Pmin than the maximum gradation value Pmax, the gradation in the non-edge area is corrected in the positive direction so that the carry gradation CX is not included in the non-edge area. ing. The correction coefficient Ca in this case is Ca
= Cx-Pmin. As can be seen from FIG. 9B showing the corrected luminance value, the gradation adjustment unit 45 sets Ca
By adding, the carry gradation is not included in the non-edge region.

In the case of FIG. 10 described above, since the carry gradation CX is closer to the maximum gradation value Pmax than the minimum gradation value Pmin, the gradation in the non-edge region is negative, contrary to FIG. By carrying out the correction in the direction, the carry gradation CX is not included in the non-edge region. The correction coefficient Ca in this case is given by Ca =-(Pmax-Cx). As can be seen from FIG. 10B showing the corrected luminance value, by adding Ca, the carry gradation is not included in the non-edge region. As described above, carry in the non-edge region can be suppressed.

However, the correction coefficient Ca must be suppressed to a certain value or less so that the image does not become unnatural. Further, when the carry cannot be suppressed unless the gradation is largely changed, the gradation is not corrected because the image is affected. Furthermore, the maximum gradation value Pmax and the minimum gradation value P
When the difference between min is large, Pmax and Pmin
Since a plurality of carry gradations are included between, there is a possibility that all carry can not be avoided. In such a case, gradation correction is not performed.

In the code conversion section 27, the digital signal corrected by the gradation correction section 26 is converted into a subfield pattern. The conversion patterns of the code conversion unit 27 are the code conversion unit A12a and the code conversion unit B1 shown in FIG.
2b, or a conversion pattern that is simply assigned as a power of 2, may be adopted.

The field memory unit 14 according to the first embodiment.
Similarly, the code-converted subfield patterns are alternately stored in the two field memories in the field memory unit 14. Each bit of the subfield pattern is, for example, bb0, bb1, bb2, bb3, bb4, bb5, bb
6, bb7, bb8, first, during the address period of SF0, the field memory unit 14 is controlled under the control of the control unit 4.
From subfield pattern bit bb0 is drive unit 15
Through PDP16.

After sequentially writing bb0 for all pixels, the pixel of bb0 = 1 in the PDP 16 emits light during the subsequent sustain discharge period. Similarly, for SF1 to SF8, bb1 to bb8 are P through the driving unit 15 in the address period, respectively.
It is written in DP16 and emits light during the subsequent sustain discharge period.
Since the light emitting operation by the field memory unit 14, the driving unit 15, and the PDP 16 is the same as that of the conventional display device 100 shown in FIG. 13, detailed description thereof will be omitted.

As described above, according to the display device of the fourth embodiment, as in the first embodiment, the cause of the occurrence of the pseudo contour of the moving image is caused inside the non-edge region which is the smooth portion in the image. It is possible to suppress the carry of the subfield.

In the non-edge region, it is highly possible that the carry of the subfield can be avoided by the change of the gradation in a slight range. Further, in a normal image, when attention is paid to a portion where the gradation changes smoothly, it is often within a relatively narrow gradation range.
There are few cases where there are a plurality of carry gradations included between Pmin and Pmin. In the display device according to the fourth embodiment,
By utilizing these properties, carry gradation is avoided by slight gradation correction, and carry of subfields with high emission brightness is suppressed, thereby preventing a pseudo contour of a moving image.

Further, in the display devices of the first to third embodiments, a plurality of suitable subfield patterns are indispensable, but the display device of the fourth embodiment only has the carry suppression processing section and the signal delay section. Since the improvement of the pseudo contour of the moving image is realized, it can be realized by adding a slight change in the circuit to the normal display device,
It is possible to adapt to a display device that is already in use.

Embodiment 5. In the display device 52 according to the fourth embodiment, the gradation correction unit 26 (FIG. 7) performs gradation correction by performing addition and subtraction only.
By performing a more complicated correction calculation, the image of the correction result can be made more natural.

The display device of the fifth embodiment has exactly the same basic configuration as the display device 52 of the fourth embodiment shown in FIG. 7, but the gradation correction unit indicated by 26 'in FIG. Since only the correction calculation method is different from that of the fourth embodiment, the block diagram of FIG. 7 and FIG.
The difference will be mainly described with reference to the graphs of FIG.

The graph of FIG. 11 corresponds to the graph of FIG. 9 described in the fourth embodiment, and is an explanatory diagram for explaining the contents of the gradation correction in the present embodiment for the same input. FIG. 6A is a graph showing the brightness value before correction, and FIG. 7B is a graph showing the brightness value after correction. Therefore, FIG.
The graphs (a) and (b) of No. 1 are the same as in FIG.
The case where (Pmax-CX)> (CX-Pmin) is shown.

At this time, the gradation correction unit 26 'has the same structure as shown in FIG.
, The output grayscale value P of the pixel inside the non-edge region
Out is compressed so as to satisfy Pmax ≧ Pout ≧ CX. Therefore, when the input gradation value is Pin, the output gradation value Pout is Pout = (Pin−Pmin) × (Pmax−CX)
Calculated by the calculation of / (Pmax-Pmin) + CX and output. As a result, the brightness at the end portion of the non-edge region becomes the same value as before correction, and more natural correction is performed.

On the other hand, the graph of FIG. 12 corresponds to the graph of FIG. 10 described in the fourth embodiment and is an explanatory diagram for explaining the contents of the gradation correction in the present embodiment for the same input. FIG. 7A is a graph showing the brightness value before correction, and FIG. 7B is a graph showing the brightness value after correction. Therefore, each graph in FIG. 12 before correction shows the case of (Pmax−CX) ≦ (CX−Pmin), as in FIG. 10A.

At this time, the gradation correction unit 26 'has a structure shown in FIG.
, The output grayscale value P of the pixel inside the non-edge region
Out is compressed so as to satisfy CX ≧ Pout ≧ Pmin. Therefore, when the input gradation value is Pin, the output gradation value Pout is Pout = (Pin−Pmin) × (CX−Pmin)
Calculated by the calculation of / (Pmax-Pmin) + Pmin and output. As a result, the brightness at the start portion of the non-edge region becomes the same value as before correction, and more natural correction is performed.

As described above, according to the display device of the fifth embodiment, the same effect as that of the display device of the fourth embodiment described above can be obtained, and the correction amount can be suppressed to the minimum. It is possible to make various corrections.

[0161]

According to the display device of the first, seventh and thirteenth aspects, a carry of a subfield which causes a pseudo contour of a moving image is generated inside a non-edge region which is a smooth portion in an image. Can be suppressed. Also,
In a normal image, the non-edge area where the gradation changes smoothly is often within a comparatively narrow gradation range, and the subfield sequence is selected so that carry does not occur in the subfield. It is more likely to be possible.

According to the display device of the second aspect, since it is composed of two subfield sequences, it is possible to obtain the effect of reducing the moving image pseudo contour with a relatively simple circuit configuration.

In the display device according to the third aspect of the invention, in the subfield series of the two series, the carry positions of the relatively large gradation weights are alternately arranged in the respective series, so that the non-edge regions are displayed. There is a high possibility that carry can be avoided, and there is an effect of further reducing the moving image pseudo contour.

According to the display device of the fourth aspect, since the subfield sequence is made up of three or more sequences, the possibility of sequence selection is expanded, and carry can be further avoided in the non-edge region. In addition to increasing the possibility, the effect of suppressing the generation of the moving image pseudo contour in the portion other than the non-edge region is also achieved, and the effect of further reducing the moving image pseudo contour is obtained.

According to the display device of the fifth aspect, the process of extracting the non-edge region is performed in units of one field. Therefore, even when displaying an object that moves not only in the horizontal direction but also in the vertical direction, a moving image pseudo is displayed. It has the effect of reducing the contour.

According to the display device of the sixth aspect, since the process of extracting the non-edge region is performed for each line, the circuit scale can be further reduced and the moving image pseudo contour can be reduced in the low cost display device. effective.

According to the display device of the eighth aspect, even if the carry of the subfield cannot be prevented inside the non-edge region, the integration effect of the human visual sense in the spatial direction is obtained as in the conventional display. , The false contours of the moving images perceived in the respective sequences are averaged to reduce the false contours of the moving image on the display.

According to the display device of the ninth, tenth and thirteenth aspects, since the carry of the subfield is suppressed by correcting the input video signal, the subfield pattern is displayed in the conventional display device. There is an effect of reducing the false contour of the moving image by making a small change to the conventional display device without changing the above.

According to the display device of the eleventh aspect, in addition to the effect of the ninth aspect, when paying attention to the non-edge region, the gradation range is often relatively narrow. By carrying out the correction, carry gradation can be avoided and carry in the sub-field can be suppressed.

According to the display device of the twelfth aspect, in addition to the effect of the ninth aspect, the correction amount can be suppressed to the minimum, so that more natural correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a display device 50 according to a first embodiment of the present invention.

2 is a circuit block diagram showing an internal configuration of a gradation range calculation unit 8 of the display device 50. FIG.

3 (a) and 3 (b) are code conversion units A, respectively.
12a is a diagram showing a configuration of a subfield sequence stored in a code conversion unit B12b. FIG.

FIG. 4 is an explanatory diagram of a subfield sequence selection method according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a display device 51 according to a second embodiment of the present invention.

FIG. 6 is a circuit block diagram showing an internal configuration of a gradation range calculation unit 8 ′ according to the third embodiment.

FIG. 7 is a block diagram showing a configuration of a display device 52 according to a fourth embodiment of the present invention.

FIG. 8 is a circuit block diagram showing an internal configuration of a gradation correction unit 26 of a display device 52 according to a fourth embodiment.

9A and 9B are explanatory diagrams for explaining a gradation correction method using the gradation correction unit 26 according to the fourth embodiment.

10A and 10B are explanatory diagrams for explaining a gradation correction method using the gradation correction unit 26 according to the fourth embodiment.

11A and 11B are explanatory diagrams for explaining a gradation correction method using the gradation correction unit 26 ′ according to the fifth embodiment.

12A and 12B are explanatory diagrams for explaining a gradation correction method using the gradation correction unit 26 ′ according to the fifth embodiment.

FIG. 13 is a block diagram showing a main configuration of a conventional display device.

FIG. 14 is a diagram showing a light emission sequence on the screen of the PDP when no countermeasure is taken for a moving image pseudo contour phenomenon in which gradation changes smoothly.

FIG. 15 is a state explanatory view for explaining a moving image pseudo contour phenomenon in a conventional display device.

FIG. 16 shows an image in which a moving image pseudo contour phenomenon occurs,
FIG. 6 is a diagram showing a relationship between a retina position and a perception amount of brightness when viewed by a human.

FIG. 17 is a diagram showing a light emitting sequence in one field period in the case where a countermeasure against a moving image pseudo contour is taken in a conventional display device.

FIG. 18 is a pattern diagram showing an example of a subfield sequence that complies with the “carry rule” in a conventional display device.

FIG. 19 shows a conventional display device as shown in FIG.
FIG. 8 is a state explanatory view for explaining a moving image pseudo contour phenomenon in the case of using the sequence of FIG.

FIG. 20 shows a conventional display device as shown in FIG.
FIG. 6 is a diagram showing the relationship between the retina position and the amount of perceived brightness when a human sees the image of FIG.

FIG. 21 is a block diagram showing another configuration of a conventional display device.

22 (a) and (b) are pattern diagrams showing an example of two series A and series B according to the "carrying rule" in the conventional display device.

FIG. 23 shows a conventional display device as shown in FIG.
11 is a state explanatory view for explaining a moving image pseudo contour phenomenon in a series B in the same image and gradation as FIG.

FIG. 24 shows a conventional display device shown in FIG.
FIG. 6 is a diagram showing the relationship between the retina position and the amount of perceived brightness when a human sees the image of FIG.

FIG. 25 is an explanatory diagram showing which selection is used to display each pixel on the screen by the series A or series B subfield pattern.

[Fig. 26] Fig. 26 is a diagram showing the effect of reducing a false contour of a moving image when two sequences are switched and displayed on a conventional display device.

[Explanation of symbols]

1 input terminal, 2 input terminal, 3 A / D converter,
4 control unit, 5 carry suppression processing unit, 6 edge detection unit, 7, 7'non-edge region extraction unit, 8, 8 '
Gradation range calculation unit, 9 series selection control unit, 10, 10
′ Signal delay unit, 11 code conversion unit, 12a code conversion unit A, 12b code conversion unit B, 13 code conversion selection unit, 14 field memory unit, 15
Drive unit, 16 PDP, 18 control unit, 20
Control unit, 21 sequence selection control unit, 22 code conversion unit group, 23 code conversion selection unit, 25 carry suppression processing unit, 26 gradation correction unit, 27 code conversion unit, 31 FIFO buffer, 32a, 32b register, 33 switching Switch, 34 maximum and minimum gradation value updating unit, 35 maximum and minimum gradation value reading unit, 41
FIFO buffer, 43 Carry determination section, 44
Correction coefficient calculation unit, 45 gradation adjustment unit, 50, 51,
52 display device.

Claims (13)

[Claims] 1. A gradation value of each pixel is represented by a u-bit digital code sequentially weighted by a predetermined relative ratio, and one field period has a light emission period according to the relative ratio.
A sub-field of which a corresponding bit in each sub-field is in a predetermined state to cause each pixel to emit light and display gray levels, wherein the relative ratio has bits that do not follow a power of two. , A code conversion means capable of digitally encoding the gradation value in a selected subfield series among a plurality of subfield series having different carry gradation values, and an image by an input video signal Assuming that, a non-edge area detection unit that detects one or a plurality of non-edge areas in which the gradation change is gentle for each predetermined range, and each non-edge area in each non-edge area. A gradation range calculating means for sequentially detecting and storing the maximum value and the minimum value of the gradation of the pixel; and the maximum value among the plurality of subfield series. To preferentially select a subfield sequence in which the carry gradation does not exist in each bit whose weighting by the relative ratio is a predetermined value or more within the gradation range of the non-edge region being processed which is determined by the minimum value. A sub-field sequence selection unit for controlling the code conversion unit, and a gradation value of the input video signal are sequentially input, and each gradation value of the non-edge region being processed is digitally input by the selected sub-field sequence. A display device, comprising: a signal delay unit that delays an input grayscale value for a predetermined time so as to be encoded and outputs the delayed grayscale value to the code conversion unit. 2. The display device according to claim 1, wherein the plurality of subfield sequences are two sequences. 3. The display device according to claim 2, wherein in the two series, the carry gradations are configured to appear alternately in magnitude of the value. 4. The display device according to claim 1, wherein the plurality of subfield sequences are three or more sequences. 5. The display device according to claim 1, wherein the predetermined range is one field. 6. The display device according to claim 1, wherein the predetermined range is one line. 7. The code conversion means comprises a plurality of code conversion units for digitally converting the input grayscale values in different subfield series, and a code conversion selection unit for selecting one code conversion unit. 2. The display device according to claim 1, wherein the selected code conversion unit outputs a digital code converted into a digital code. 8. The subfield series selecting means selects the plurality of subfield series for each predetermined pixel unit when the subfield series in which the carry gradation does not exist cannot be found in the gradation range. To select sequentially,
The display device according to claim 1, wherein the code conversion means is controlled. 9. The code conversion means represents the gradation value of each pixel by a p-bit digital code sequentially weighted at a predetermined relative ratio, and one field period has a subfield of p having a light emission period according to the relative ratio. Split into
In a display device in which each pixel in which a corresponding bit in each subfield is in a predetermined state emits light to display a gradation, when an image based on an input video signal is assumed, the gradation change is 1 or Non-edge region detection means for detecting a plurality of non-edge regions, and for each of the non-edge regions, the maximum value and the minimum value of the gradation of each pixel in each non-edge region are sequentially detected and stored. And a gradation range calculation means for performing, within the gradation range of the non-edge region being processed that is determined by the maximum value and the minimum value, the carry gradation at each bit whose weighting by the relative ratio is a predetermined value or more. If present, the gradation value is corrected so that the carry gradation is not included in the corrected gradation range obtained by correcting the gradation value of each pixel in the non-edge region being processed. And output to the code conversion means Display apparatus characterized by having a gradation correction means for. 10. The gradation correction means, a signal delay means for sequentially inputting the gradation values of the input video signal, delaying them for a predetermined time and outputting them, the gradation range and the carry gradation value. 10. The display device according to claim 9, further comprising: a gradation correction unit that corrects the gradation value delayed by the signal delay unit based on the above. 11. The gradation correction unit corrects the difference between the maximum value or the minimum value of the gradation and the value of the carry gradation by adjusting the input delayed gradation value. The display device according to claim 10, wherein the display device is a display device. 12. The gradation correction unit compresses the gradation range of the input delayed gradation value by the difference between the maximum or minimum gradation value and the carry gradation value. 11. The display device according to claim 10, wherein the gradation value is corrected so that 13. The non-edge region detecting means detects an edge part where an image gradation changes abruptly, and the brightness or color changes smoothly based on the edge information from the edge detecting part. 10. The display device according to claim 1, further comprising a non-edge region extraction unit that extracts the non-edge region.